The present invention is directed to a method of in-situ cleaning and deposition of device structures in a high density plasma environment.
Plasma cleaning or etching is a process whereby a gas is subject to a radio frequency electric field in a reaction chamber to form a plasma. A plasma is a gas which contains positive, negative and neutral atoms, electrons and/or molecules including radicals and a xe2x80x9cgasxe2x80x9d of emitted photons. A chemically inert gas, such as argon, is ionized to form the plasma and accelerated to impinge on a device structure so that material is removed from the surface of the device structure by momentum transfer, a process similar to sand blasting. The ions/radicals interact with the surface of the atoms or molecules within the material to be cleaned or etched and in some circumstances forming a volatile by-product which is subsequently removed from the reaction chamber.
One form of cleaning uses a high density plasma source for bombarding the device structure. High density plasma cleaning utilizes a lower direct current (DC) offset voltage to accelerate the ionized particles toward the device structure than conventional plasma cleaning techniques. The lower offset voltage allows for cleaning with less chance of device damage often caused by high energy ion impacts.
Sputter deposition refers to a mechanism in which atoms are dislodged from a target material by collision with high energy particles. The sputtering process involves generating and directing ions at a target. The momentum of ions incident on the target is transferred to the surface atoms of the target material, causing their ejection. A portion of the ejected sputtered species from the target are accelerated in an electric field toward a device structure, although the vast majority of the sputtered species are neutral. The ejected atoms from the target condense on the surface of the device structure to form the desired film.
Cleaning and sputter deposition are typically performed in separate chambers requiring the device structures to be moved from chamber to chamber. Handling of the device structures may expose them to contamination, the formation of native oxide thereon, or damage, and generally requires an extra chamber.
The present invention includes a method for in-situ plasma cleaning and sputter deposition in a single high density plasma chamber during the processing of a device structure. The present method is particularly useful for cleaning high aspect ratio device structures.
A device structure is located in a reaction chamber containing a sputter target. A high density plasma containing ionized gas particles is generated in the reaction chamber. The ionized gas particles are accelerated toward the device structure during a cleaning phase. At least a portion of by-products produced during the cleaning phase are evacuated from the reaction chamber. The ionized gas particles are then accelerated toward the sputter target during a deposition phase so that a layer of sputter target material is deposited on at least a portion of the device structure.
The cleaning phase may be divided into a first cleaning phase during which no power is applied to the sputter target and a second cleaning phase during which power is supplied to the sputter target sufficient to remove at least a portion of by-products deposited on the sputter target during the first cleaning phase. The step of providing power to a sputter target preferably includes the step of providing power at a level that results in substantially no deposition of the sputter target material on the device structure. Power of about 0-1 watt/cm2 is typically provided to a sputter target during the second cleaning phase.
In an alternate embodiment, the ion containing gas used during the cleaning phase is different from the ion containing gas used during deposition phase.
Low power in the range of about 0 to 1 watt/cm2 may be applied to the sputter target during a second cleaning phase. Pressure within the reaction chamber is preferably maintained in the range of about 10 to 100 mtorr during the cleaning phase. The step of biasing the device structure includes the step of providing a bias in the range of about 50 to 150 volts. The high density plasma generally has at least 1011 particles per cubic centimeters. The sputter target is generally selected from the group consisting of Ti, Pt, Mo, W, Au, Ni, Co, Al, Ta, Si and combinations thereof.